Estimated Effectiveness of JYNNEOS Vaccine in Preventing Mpox: A Multijurisdictional Case-Control Study — United States, August 19, 2022–March 31, 2023
Authors: Alexandra F. Dalton, Alpha Oumar Diallo, Anna N. Chard, Danielle L. Moulia, Nicholas P. Deputy, Amy Fothergill, Ian Kracalik, Christopher W. Wegner, Tiffanie M. Markus, Preeti Pathela, William L. Still, Sam Hawkins, Anil T. Mangla, Nivedita Ravi, Erin Licherdell, Amber Britton, Ruth Lynfield, Melissa Sutton, AmberJean P. Hansen, Gabriela S. Betancourt, Jemma V. Rowlands, Shua J. Chai, Rebecca Fisher, Phoebe Danza, Monica Farley, Jennifer Zipprich, Gregory Prahl, Karen A. Wendel, Linda Niccolai, Jessica L. Castilho, Daniel C. Payne, Amanda C. Cohn, Leora R. Feldstein, Kayla Saadeh, Robert E. Snyder, Madeline Anderson, Vanessa Aryana Anguiano, Joelle Nadle, Gretchen Rothrock, Sydney Jones, Lauren Duval, Rachel Herlihy, Ginger Stringer, Robyn Weber, Quyen Phan, Lynn Sosa, James Meek, Michelle Lee, Allison S. Morrow, Christina Willut, Jesse Carlson, Kevin Kamis, Masayo Nishiyama, Gena Simien, Jonathan Colasanti, Tamsin M. van der Woude, Roxanne Archer, Lauren Finn, Jane Lam, Bret Moulton, Erin Peterson, Robert Bolan, Gabriel Garcia-Lopez, Kathryn Como-Sabetti, Anna Ruff, Dakota Schneider, Tracy Robinson, Bridget J. Anderson, Kerianne Engesser, Suzanne McGuire, Adam Rowe, Christopher Pride, Jaxon Mitchell, Yelena Tourkina, Paul R. Cieslak, Mary Margaret Fill, Caleb Wiedeman, Ghinwa Dumyati, Christina Felsen, Joseph A. Lewnard, Bentley Akoko, Kristyne Mansilla-Dubon, Danielle Ndi, H. Keipp Talbot, Sweta Tiwari, Dayna Wyatt
Journal: MMWR Morbidity and Mortality Weekly Report (2023)

As of March 31, 2023, more than 30,000 monkeypox (mpox) cases had been reported in the United States in an outbreak that has disproportionately affected gay, bisexual, and other men who have sex with men (MSM) and transgender persons (1). JYNNEOS vaccine (Modified Vaccinia Ankara vaccine, Bavarian Nordic) was approved by the Food and Drug Administration (FDA) in 2019 for the prevention of smallpox and mpox via subcutaneous injection as a 2-dose series (0.5 mL per dose, administered 4 weeks apart) (2). To expand vaccine access, an Emergency Use Authorization was issued by FDA on August 9, 2022, for dose-sparing intradermal injection of JYNNEOS as a 2-dose series (0.1 mL per dose, administered 4 weeks apart) (3). Vaccination was available to persons with known or presumed exposure to a person with mpox (postexposure prophylaxis [PEP]), as well as persons at increased risk for mpox or who might benefit from vaccination (preexposure mpox prophylaxis [PrEP]) (4). Because information on JYNNEOS vaccine effectiveness (VE) is limited, a matched case-control study was conducted in 12 U.S. jurisdictions,† including nine Emerging Infections Program sites and three Epidemiology and Laboratory Capacity sites,§ to evaluate VE against mpox among MSM and transgender adults aged 18-49 years. During August 19, 2022-March 31, 2023, a total of 309 case-patients were matched to 608 control patients. Adjusted VE was 75.2% (95% CI = 61.2% to 84.2%) for partial vaccination (1 dose) and 85.9% (95% CI = 73.8% to 92.4%) for full vaccination (2 doses). Adjusted VE for full vaccination by subcutaneous, intradermal, and heterologous routes of administration was 88.9% (95% CI = 56.0% to 97.2%), 80.3% (95% CI = 22.9% to 95.0%), and 86.9% (95% CI = 69.1% to 94.5%), respectively. Adjusted VE for full vaccination among immunocompromised participants was 70.2% (95% CI = -37.9% to 93.6%) and among immunocompetent participants was 87.8% (95% CI = 57.5% to 96.5%). JYNNEOS is effective at reducing the risk for mpox. Because duration of protection of 1 versus 2 doses remains unknown, persons at increased risk for mpox exposure should receive the 2-dose series as recommended by the Advisory Committee on Immunization Practices (ACIP),¶ regardless of administration route or immunocompromise status.